Spring Chinook
Spring Chinook
Background
The run of spring Chinook salmon in the Coquille River is extremely depressed. Currently the population may be as low as 200 individuals. The historical inventory basis for spring Chinook salmon in the system is very poor, but this stock may have numbered upwards of a couple thousand spawners in the early 1900s. The run has declined to such a low level that its future viability is now immediately at risk. The population is on ODFW’s list of stocks of concern.
The primary influence depressing the population of spawning spring Chinook salmon in the Coquille River is poaching and harassment during the summer-maturation period in the river. For decades tremendous amounts of poaching have been directed toward this stock. The spring Chinook salmon over-summer in large deep holes where the water in the South Fork is clear and the fish are easily observed. AS a result, they are easily harassed. Steps have been taken to reduce this illegal and extremely damaging activity by attempting to educate the public about the value of spring Chinook salmon in the Coquille River, particularly on the South Fork around Powers. Posters and numerous presentations have been given to the public to communicate the value of the spring Chinook and the need to protect the spawning stock. Efforts should continue to influence the public to attempt to reduce illegal activities by educational signs and more enforcement. Starting in 1992 the angling regulations will not allow Chinook salmon to be harvested upstream from the confluence of the North and South forks from March 31 to September 30 in an attempt to give more protection to the spawning population. Additional fishing restrictions and the possibility of complete closure to fishing in upstream area of the South Fork have been discussed to aid in enforcement and protection of spring Chinook salmon.
Habitat in the Coquille River for spring Chinook salmon does not appear to be any more limiting than that for the abundant fall Chinook salmon using the same spawning and rearing areas. The river system seems to have an abundance of large pools for the adults to over-summer although more cover and hiding areas within those pools for the adults would be beneficial. Overall amount of spawning habitat is not limited, although fall Chinook salmon which spawn later may dig up the spawning redds of the spring Chinook salmon. On the other hand, spawning habitat for spring Chinook salmon may not be distributed in the best areas to maximize the use of the most desirable juvenile habitat by emerging fry. This is particularly true in the upper East and South forks. Competition with fall Chinook salmon in the limited freshwater and estuarine rearing areas could also be occurring. The large abundance of juvenile fall Chinook salmon may give them a numerical advantage although juvenile spring Chinook salmon emerge from the gravel prior to juvenile fall Chinook salmon and individual fish should have a size advantage.
Water quality, particularly temperature, plays a role in adult survival. Coulmnaris, a disease prevalent in salmonids in warm water, have been known to cause mortality in adults. However, high temperature may have its greatest influence on the juveniles attempting to rear in freshwater areas until autumn. Most of the mainriver rearing areas of the Coquille River are quite warm forcing most juvenile Chinook salmon to move downstream from freshwater rearing areas into tidewater during the summer months. Water temperatures in the South Fork below Powers often exceed 70 F at mid-day and approach lethal levels. Few salmonids of any kind were found residing in a 6.5-mile section of the South Fork around Powers in a survey in 1989 by USFS biologists. On the otherhand, juvenile Chinook salmon were present in cooler upstream areas within the Siskiyou National Forest. Based on this observation and because juvenile spring Chinook salmon emerge from the gravel sooner than fall Chinook salmon, we propose a short-term hatchbox program for one life cycle in an attempt to shift some of the natural production of spring Chinook salmon in the South Fork to the upper sections of cooler rearing habitat. Releasing fry in the Siskiyou National Forest should give them first chance at the best rearing habitat. If the program works and the juveniles are able to survive to return as adults, they will hopefully home back to those upstream areas and survive human harassment during their summer-maturation period. If that occurs, natural production should increase and the population should be able to become self-sustaining at a somewhat larger population than exists today. This effort is proposed as a one-time attempt to help rehabilitate the wild population. The wild population will likely remain at a relatively low level until water temperatures become cooler over a greater part of the freshwater rearing area, more widespread protection of maturing adults can be achieved throughout the river, and we are certain that spawning gravel is available and used in upstream areas where emerging juveniles will have the best chance of being in good rearing habitat.
Since the 1983 brood year, a hatchery smolt program has been conducted with spring Chinook salmon in the Coquille River. This has been as attempt to supplement the wild production with releases at a variety of sites around the drainage in the South Fork, East Fork, and in tidewater at Coquille River. The hatchery smolts survived well and contributed well to Oregon ocean fisheries based on coded-wire tag data from the 1983 and 1985 broods. Total survival was 1.77% and 1.79%, respectively with average contributions to Oregon of 68%, California of 22%, Washington of 3%, British Columbia of 7%, and less than 1% in Alaska. In addition to achieving fishery benefits, we initially thought that this program was good for the wild population by giving a boost to the total natural spawning population. However, we have not seen an increase in the total spawning population. Furthermore, a recent theoretical paper on genetics suggests that we may actually be doing the wild population a disservice by narrowing its genetic base with our hatchery smolt program. Because the wild population is already small, its effective breeding population is small and its genetic base is narrow. This puts the survival potential for the population at an unusually high risk from the effects of normal environmental fluctuations in both the freshwater and marine habitats. When even a small number of the wild spawners is then removed for a hatchery program, the wild population becomes smaller and its genetic base more narrow. But the big population occurs when hatchery smolts produced from a small sample of the breeding population contributes a high proportion of the genetics resources for natural spawning in a combination of wild and hatchery spawners. The net result is that the genetic variability in the breeding population goes down even farther. An examination of the hatchery programs and natural spawning population on the South Fork suggested that this detrimental process is very likely occurring.
In 1989 a total of 48 Spring Chinook salmon were captured in netting operations. This was the largest sampling in any year of brood collection. Of those sampled, 20 or about 42% were coded-wire-tagged returns from the hatchery smolt program. These returns were from a release of only 8,565 smolts produced from only five females from the 1985 brood. Sampling of adults in other years included fewer fish, but the percentage of hatchery returns ranged from 21% to 60%. This is a classic example of the type of problem outlined by Ryman and Laikre(1991) and this ratio of hatchery to wild fish is also an example of a fundamental problem for any small wild populations and the genetic concern outlined in the Wild Fish Management Policy. Based on this scenario, the hatchery smolt program for spring chinook salmon on the Coquille River should be terminated and major effort put into increasing natural production to a larger spawning population through more protection for maturing adults, increasing spawning gravel in critical upstream areas, and cooling the river for juvenile rearing. To some extent, our proposal to use hatchbox fry for one life cycle in an attempt to shift natural spawning upstream in the South Fork is also suspect from a genetic standpoint. However, these fry will be subject to natural rearing conditions, natural selection, and are likely to survive at rates like the naturally spawned wild populations(ODFW,1992).